Simulating the influence of snow surface processes on soil moisture dynamics and streamflow generation in an alpine catchment
Simulating the influence of snow surface processes on soil moisture dynamics and streamflow generation in an alpine catchment
复制标题
模拟高山流域雪面过程对土壤水分动态和水流生成的影响
DOI：
10.5194/hess-21-4053-2017
复制
发表时间：
2017
影响因子：
6.3
通讯作者：
M. Lehning
中科院分区：
文献类型：
--
作者：
N. Wever;F. Comola;M. Bavay;M. Lehning
摘要。评估高山积雪集水区的洪水风险需要了解水系中积雪、土壤和流量之间的联系。在这里，我们应用Alpine3D综合分布式模型来研究土壤湿度在瑞士Dischma集水区对降雨和融雪大流量的倾向中的作用。最近更新的基于物理的多层积雪模型SNOWPACK的土壤模块解决了Alpine3D中的表面能量和质量平衡问题，并通过在Dischma集水区内部和附近的七个站点和不同深度的土壤湿度测量进行了验证。在这样的地形中测量和模拟是困难的，因此，土壤湿度的模拟取得了不同程度的成功。模拟和实测土壤湿度之间的差异主要是由于高估了土壤冻结和Alpine3D模型中缺乏地下水描述。两者都被发现对土壤湿度测量有影响。利用Alpine3D模拟作为空间显式水文响应模型的地表方案，采用行时分布方法对汇流和基流进行了径流模拟。在Alpine3D模型中，利用30 cm深度的土壤水通量驱动水文响应模型时，径流模拟结果与观测结果吻合较好。当使用2 cm土壤水通量时，性能下降，因此基本上忽略了土壤过程。这表明，在了解高山地区积雪径流与降雨和集水区流量之间的关系时，土壤湿度的作用是重要的。然而，使用60 cm深度的土壤水通量来驱动水文响应模型也降低了其性能，这表明地表模拟中存在最佳土壤深度，径流动力学仅受浅层土壤控制。基于高降雨和融雪事件测量的径流系数（即降雨量与流量之比）被发现依赖于事件开始时模拟的初始土壤湿度状态，进一步说明了土壤湿度对流域水文过程的重要作用。使用模拟流量的径流系数再现了这种依赖性，这表明Alpine3D模型框架可以成功地应用于评估集水区对融雪和降雨事件的洪水风险的倾向性。
Abstract. The assessment of flood risks in alpine, snow-covered catchments requires an understanding of the linkage between the snow cover, soil and discharge in the stream network. Here, we apply the comprehensive, distributed model Alpine3D to investigate the role of soil moisture in the predisposition of the Dischma catchment in Switzerland to high flows from rainfall and snowmelt. The recently updated soil module of the physics-based multilayer snow cover model SNOWPACK, which solves the surface energy and mass balance in Alpine3D, is verified against soil moisture measurements at seven sites and various depths inside and in close proximity to the Dischma catchment. Measurements and simulations in such terrain are difficult and consequently, soil moisture was simulated with varying degrees of success. Differences between simulated and measured soil moisture mainly arise from an overestimation of soil freezing and an absence of a groundwater description in the Alpine3D model. Both were found to have an influence in the soil moisture measurements. Using the Alpine3D simulation as the surface scheme for a spatially explicit hydrologic response model using a travel time distribution approach for interflow and baseflow, streamflow simulations were performed for the discharge from the catchment. The streamflow simulations provided a closer agreement with observed streamflow when driving the hydrologic response model with soil water fluxes at 30 cm depth in the Alpine3D model. Performance decreased when using the 2 cm soil water flux, thereby mostly ignoring soil processes. This illustrates that the role of soil moisture is important to take into account when understanding the relationship between both snowpack runoff and rainfall and catchment discharge in high alpine terrain. However, using the soil water flux at 60 cm depth to drive the hydrologic response model also decreased its performance, indicating that an optimal soil depth to include in surface simulations exists and that the runoff dynamics are controlled by only a shallow soil layer. Runoff coefficients (i.e. ratio of rainfall over discharge) based on measurements for high rainfall and snowmelt events were found to be dependent on the simulated initial soil moisture state at the onset of an event, further illustrating the important role of soil moisture for the hydrological processes in the catchment. The runoff coefficients using simulated discharge were found to reproduce this dependency, which shows that the Alpine3D model framework can be successfully applied to assess the predisposition of the catchment to flood risks from both snowmelt and rainfall events.